Abstract

A new method for estimating the Dancoff factors in pebble beds has been developed and implemented within two computer codes. The first of these codes, INTRAPEB, is used to compute Dancoff factors for individual pebbles taking into account the random packing of TRISO particles within the fuel zone of the pebble and explicitly accounting for the finite geometry of the fuel kernels. The second code, PEBDAN, is used to compute the pebble-to-pebble contribution to the overall Dancoff factor. The latter code also accounts for the finite size of the reactor vessel and for the proximity of reflectors, as well as for fluctuations in the pebble packing density that naturally arises in pebble beds.

@article{osti_911013,
title = {Computation of Dancoff Factors for Fuel Elements Incorporating Randomly Packed TRISO Particles},
author = {J. L. Kloosterman and Abderrafi M. Ougouag},
abstractNote = {A new method for estimating the Dancoff factors in pebble beds has been developed and implemented within two computer codes. The first of these codes, INTRAPEB, is used to compute Dancoff factors for individual pebbles taking into account the random packing of TRISO particles within the fuel zone of the pebble and explicitly accounting for the finite geometry of the fuel kernels. The second code, PEBDAN, is used to compute the pebble-to-pebble contribution to the overall Dancoff factor. The latter code also accounts for the finite size of the reactor vessel and for the proximity of reflectors, as well as for fluctuations in the pebble packing density that naturally arises in pebble beds.},
doi = {10.2172/911013},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2005,
month = 1
}

The importance of an integral approach to the problem of the resonance escape probability in close-packed lattices is discussed. A review is performed of the theoretical basis for the Dancoff correction to the effective resonance integral in close-packed lattices. Emphasis is given to a physical interpretation which results in a clear understanding of the problems associated with its application. Although more questions are raised than are resolved, the solution to the problem of the determination of an effective resonance integral in a close-packed lattice is suggested with recommendations to implement ths solution. A computer code, which was written to extendmore » the results of Dancoff, is described and some results obtained from this code are pressnted. (auth)« less

Proliferation issues relating to the use of highly enriched uranium (HEU) have led to an evaluation of the fission product-SiC interaction problems that might arise if low enriched uranium (LEU) or medium enriched uranium (MEU) were used as fissile fuel in HTGR systems. Simulated Triso-coated UO/sub 2/, UC/sub 2/, and UO/sub 2//UC/sub 2/ particles mixed with varying amounts of Mo, Ru, Rh, Pd, Ag, and Cd were prepared. These fission products were chosen because, after full burnup, their concentrations are higher in LEU and MEU fuels than in HEU fuel. After the particles were heat treated in the laboratory, theirmore » behavior was examined by use of metallography, scanning electron microscopy, and electron microprobe x-ray analysis.« less

Pyrolytic carbon (PyC) is one of the important structural materials in the TRISO fuel particles which will be used in the next generation of gas-cooled very-high-temperature reactors (VHTR). When the TRISO particles are under irradiation at high temperatures, creep of the PyC layers may cause radial cracking leading to catastrophic particle failure. Therefore, a fundamental understanding of the creep behavior of PyC during irradiation is required to predict the overall fuel performance.